Heating apparatus



y 1950 J. E. LUDWIG, SR 2,508,792

HEATING APPARATUS Filed Dec. 15, 1947 INVENTOR.

JOHN E. LUDWIG 5R. BY

Patented May 23, 1950 N I TED PAT-EN T OFFICE HEATING APPARATUS I John E. Ludwig, Sin, Detroit, Mich., assignor to David-Ludwig Company, Detrdit,.Mich., a cor- V Vporation 101? Michigan .Appllcationibeeember 15, 1947, Serial No. 791,817

2 Claims. 1 "-Ihis invention relates generally to heating apparatus and refers more "particularly to improvements in forced air heating assemblies of the type embodying a blower.

In air heating equipment embodying-a blower for forcing air'to a point of demand, 'it hasbeen the custom to position an electrically operated heating element in the form of a grid at the discharge opening'of the blower, so that air issuing "from the blower passes "through the grid in heat conductingrelation thereto. Gth'er heat exchange units have been used, such for example, as coiled or serpentine tubing, either finned or plain, "and providing a circuitous passage for a heating medium.

Regardless of which specific type of heat exchange unit is selected, the latter is ordinarily so positioned with respect to the blower that air discharged from the blower mustpass'through the unit in heat conducting relation "thereto. Thus the heating 'efilciency of "assemblies embodying either of the types of heat exchange units noted'ab'ov'e depends largely 'on thesurface area of the unit available for. contact-with the air, 'andupon the length of time'the ai'rremains in theheating zone, or in otherwor'ds, upon'the velocity of the air passing through theunit. In instances where a substantial volume of air is forced through the unit at a relatively high velocity, heating units of considerable capacity and heat radiating area must he provided in order to adequately heat the air. Inasmuch as the heat exchange units are positioned in the direct path of air issuing from the blower, it follows that the heat radiating surfaces on such units obstruct the flow of airand create a -turbulence which tends to reduce air velocity. .Accordingly, the capacity of the blower must be in.- creased to compensate for the drop in velocity o'ilthe air caused by the resistance to flowof air through the unit, and the cost of the heating assembly 'is thereby greatly increased.

With the above in view, it is one of the objects of this invention to provide a forced air heater assembly having means for substantially elevate ing the temperature of the air as it approaches the blower discharge opening without obstructing or otherwise resisting the air flow. In fact with this invention the air is heated without the necessity of flowing the air in contact with heat radiating surfaces, and as a consequence, the efficiency of a heater assembly of given size to deliver the required volume of heated air at the desired velocity is greatly increased.

Another object of this invention is to provide 2 a heater assembly wherein the air discharged 'by the *blower 'is heated byintroduc'ing a stream of extremelyihot gas/into theblower casing adjacent the discharge opening, and wherein the stream of gas is caused to flow in 'the'general direction ofair fiow in the blower casing. 'Thusthestream of hot gases tends "to assist rather than obstruct the flow 'ofair whil'e heating the same, and costly heat exchange units of the general type noted above, with their accompanying disadvantages, are eliminated.

'A more detailed object of this invention is to burn a combustiblegaseous'flmixture in a "chamber and to discharge the products of combustion into the blower casing adjacent the a-ir disch'arge opening. As a result'the air passing through the blower casing to the discharge opening is efiectively heated by the products of combustion without resisting or otherwise interfering with the air flow. I

"A further feature of this invention'is toattach the burner tothe blower casing in a manner to provide a compact, self-contained unit which is relatively inexpensive to produce and does '"not' appreciably increase theovera'll dimension of the blower.

The foregoing aswell asother object's will bemade more apparent'a's this description proceeds; especially when considered in connection with the accompanying drawing, wherein:

Figure "1 is a semid'iagrammatic planview of a heater embodying the features 'ofthis invention; and V Figure 2 is a'sectional view *talrensubstantiaIIy on the plane indicated by the "line 2'--2 of Figure '1. Y

As shown in "the drawing the heater apparatus selected for "the purpose of illustrating this invention' comprises "a blower ID of the centrifugaltype and a burner; II; 'The blower ii in turn comprises 'a casing 1'2 and a fan =I'3-of' the-si rocco type. The casing I2 is preferably formed of sheet metal and may be provided with a pedestal l4 enabling supporting the casing on suitable supporting structure not shown herein. An inlet opening for air I5 is formed in one side of the casing, and an outlet'opening I6 is formed in the front wall of the casing. As shown particularly in Figure 2 of the drawing, the inlet opening 15 is connected to the outlet opening I6 by a passage I! which extends around the periphery of the fan l3 and in accordance with conventional practice, gradually increases in cross sectional area in the direction of rotation of the fan to the outlet opening l6.

The fan f3 comprises a cage provided with the usual vanes l8 and is secured at its center to a drive shaft iii. The drive shaft l9 extends through the side of the casing opposite the inlet opening I5, and is journaled on a suitable support 20. The outer end of the drive shaft is connected to a suitable prime mover, such for example, as an electric motor 2|.

The fan 13 is driven by the motor 2| in the direction of the arrow 22 in Figure 2 of the drawing, and in response to this rotation, the vanes l 8 draw air through the inlet opening I and discharge the air into the passage l1. The air discharged into the passage i1 is also moved by the fan through the passage to the outlet opening it and is discharged from the latter in the form of a blast or stream of air.

The purpose of the burner H is to heat the air flowing through the passage 11 to the discharge or outlet opening it. The burner H comprises a housing 23 preferably formed of sheet metal and secured to the rear wall of the casing l2 adjacent the top of the latter directly opposite the outlet opening 15. The front end of the housing is open and communicates with the passage H in the blower casing [2 through a slot or opening 24 formed in the rear wall of the casing 52. The housing I3 is preferably lined with a suitable refractory material 25 adapted to withstand extremely high temperatures and having a passage 26 therethrough communicating at the front end with the interior of the housing 12 through the opening 24. The rear or outer end of the passage 26 communicates with the interior of a combustion chamber 21 formed in a refractory body 28. The body 28 is enclosed by a metal case 29, and the latter is secured to the rear wall 30 of the housing 23.

The combustion chamber 21 is connected to a fuel supply conduit 3|, and the latter in turn communicates with a source of fuel supply not shown. The fuel employed may be natural or artificial gas or oil or may be any suitable gaseous or liquid fuel, as desired. In any case the fuel employed is mixed with the proper amount of air by means of a suitable mixer indicated in the drawing by the numeral 32 and connected to an air supply through a conduit 33. The combustible mixture thus obtained is introduced to the combustion chamber 21, and is ignited in the latter by a suitable pilot. The pilot is connected to the lower end of a conduit 34 which projects into the combustion chamber 21 through an opening formed in one side of the latter, and is connected adjacent the upper end to the source of fuel supply through a conduit 35. The proper amount of air is mixed with the fuel by a suitableair connection indicated by the numeral 36. If desired an electrically operated ignition device 31 may be provided in the combustion chamber for igniting the pilot when it is desired to initially start operation of the blower.

As the fuel mixture in the chamber 21 burns, the gases expand and the products of combustion are projected into the casing l2 through the passage 26 in the form of a. flame 31. As shown in Figure 2 of the drawing, the blast of intensely hot gases, or in other words, the flame 31, is projected into the air passage I! in the general direction of flow of the air through the passage to the outlet opening IS in the casing 12. Thus the products of combustion not only substantially elevate the temperature of the air flowing through the passage I! to the outlet opening IS in the casing 12, but in addition, accomplish this result without interrupting or resisting movement of the air through the passage l1. Also due to the intense heat of the gaseous products of combustion discharged into the blower, the temperature of the air is elevated substantially above the temperatures heretofore obtainable by passing the air through heat exchange units. Moreover the capacity of the blower need not be enlarged to compensate for the resistance offered by conventional heat exchange units to the flow of air therethrough. In addition the burner II is of very simple construction, and may be produced at a cost considerably less than orthodoxheat exchange units.

What I claim as my invention is:

1. An air heater comprising a casing having an axial inlet and tangential outlet, a rotary centrifugal impeller within said casing, an 6X9 tension of said casing opposite said tangential, outlet, a refractory lining within said extension. and a burner within said lining for directing its,

flame and products of combustion within and in the direction of air current discharged through said tangential outlet.

2. An air heater comprising a casing having liner directed to discharge its flame and products of combustion within and in the same direction as the air discharged through said tangential out-. let.

JOHN E. LUDWIG, SR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 941,630 Edison Nov. 30, 1909 1,669,614 Hext May 15, 1928 1,857,447 Engels May 10, 1932 2,000,733 Avery May 7, 1935 Engels Mar. 8, 1930 

